Wind turbines blades are typically joined to the wind turbine hub with a mechanical multipoint joints, prestressed with stressed screws. Likewise, the blades divided into several modules can be assembled with mechanical joints between metal parts called inserts. The basic function of these blade root joint elements and the intermediate joint elements is transferring traction and/or compression loads transmitted from the blade laminations.
The nearest state-of-the-art corresponds to patent EP 18789155 where metal inserts axially housed in blade module walls are presented, where this wall is made of a composite lamination with a series of holes. The structural joint between the composite material and the inserts is carried out with chemical means (adhesive) and is defined as a single shear joint, as each side of the insert is in contact with one of the sides of the hole in the composite material.
However, the transfer of traction and/or compression loads produced in the blade's laminations as a consequence of the loads caused in the blade by the action of the wind are very big. This problem could be solved reinforcing the module walls with more fibre and large inserts, but this excess weight in the blades would unacceptably increase loads in the wind turbine.